Cancerous anemia is an anemia specific to cancer patients, and is known to be an anemia largely different to generally-known iron-deficiency anemia and renal anemia. It is known that, although differing in degree, actually 80% of people suffering from cancer become cancerous anemic and the anemic symptoms worsen with cancer progression, and that anemia progresses further by anticancer drugs and radiation treatment. Cancerous anemia has become a major problem since it greatly reduces the quality of life of cancer patients.
Among that considered to be cancerous anemia, although examples of iron-deficiency anemia caused by bleeding from cancer sites are known, such is only a small portion, and the cause of most cancerous anemia is still unknown. According to Ouchi et al., although the mechanism of cancer secreting an anemia inducing factor to hemolyze red blood cells has been proposed and studied, the anemia inducing factor has still not been specified (for example, refer to Non-Patent Document 1).
In contrast, although iron-deficiency anemia in most cases is resolved by the administration of an iron supplement, iron supplements rarely show effects for cancerous anemia. Also, iron supplements are rarely used for cancerous anemia for the reason that iron promotes cancer growth.
On the other hand, it is known that the cause of renal anemia is reduction in the production of erythropoietin, which is a hematopoietic factor that promotes differentiation to red blood cells. Compounds which stimulate erythropoietin, derivatives thereof, and erythropoietin receptors have been developed and are in practical use. However, since examples in which reduction of the concentration of erythropoietin has occurred are not known for normal cancerous anemia patients, it is considered that the causes of renal anemia and cancerous anemia are completely different.
Regardless of this, many attempts have been made to use erythropoietin for the symptomatic therapy of cancerous anemia. However, although small improvement in anemia has been seen for cancerous anemia which has worsened by some anticancer drugs and radiation treatment, permission has been cancelled in the United States of America since the survival rate of the administered group was less than the placebo group, and approval has been denied in Japan. It has been reported that, according to the analysis of the experimental results, the incidence rate of thrombosis and vascular system disorder in the administered group was high, and tumor progression was promoted (for example, refer to Non-Patent Document 2).
Accordingly, although blood transfusion has been performed as symptomatic therapy in the treatment of cancerous anemia, blood transfusion has the risk of various infectious diseases and there is also the problem of iron repletion. Furthermore, since the costs are high and blood supply is limited, there is a desire for the development of an agent for ameliorating cancerous anemia and an agent for preventing cancerous anemia.